The role of smectite composition on the hyperalkaline alteration of bentonite

摘要: Abstract Cementitious materials will act as a source of alkaline fluids modifying the mineralogy, pH and physical–chemical properties bentonite barriers implemented for long-term pollutants retention. A series reactivity experiments in batch reactors at 175 °C were performed nearly 15 months to evaluate chemical mineralogical responses four different bentonites with potential use buffer against hyperalkaline K–Na–OH-type solution. This solution simulates early stage an ordinary Portland cement leaching clay hosted nuclear waste repository. The tested three montmorillonitic bentonites: MX-80 (Wyoming type, USA), FEBEX (Almeria, Spain), from Chile (MMT); saponitic el “Cerro del Aguila” (Toledo, Spain). Partial dissolution smectite precipitation secondary phases such analcime K-feldspar (sanidine or orthoclase) found reaction products dioctahedral smectite-based whereas trioctahedral character showed more resistance alteration. In addition, mixed-layered illite/smectite (I–Sm) interstratification was observed degrees order. most heterogeneous octahedral sheet significant Fe Mg occupations (FEBEX bentonites) altered produce R0 random I–Sm (60–40% I), virtually ideal Al–Mg (MMT bentonite) saponite R ≥ 1 ordered (> 80% I). (CEC SSA) also differently bentonites. methodology used this work is thought develop direct comparison performance hazardous evaluation other basic hydro-mechanical should be further evaluated serve indicator stability reactive environments.